Acoustical tone control for wearable hearing aids



July 10, 1956 w. R. WALTERS 2,754,365

ACOUSTICAL TONE CONTROL FOR WEARABLE HEARING AIDS Filed Sept. 15. 1952 2Sheets-Sheet 1 INVENTOR.

War/v03 Wefiaj /7 BY July 10, 1956 w. R. WALTERS ACOUSTICAL TONE CONTROLFOR WEARABLE HEARING AIDS Filed Sept. 15, 1952 2 Sheets-Sheet 2 0 u z zW FRf'QUE/YCY //Y CR6.

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wa e/Z2 m 20 BY WW1 nited States Patent 4 ACOUSTICAL TONE CONTROL F QRWEARABLE HEARING AIDS Warren R. Walters, Natiek, Mass, assignor to TheMaico Company, incorporated, Minneapolis, Minn., a corporation ofMinnesota Application September 15, 1952, Serial No. M9584 Claims. (Cl.179-107) My present invention relates to improvements in wearablehearing aids, and more particularly to that type of hearing aidstructure comprising an air conduction type audio reproducer or receiverlocated remotely from the wearers ear and is connected to an auditorycanal of the car by a flexible sound conduit or tube and a suitable earpiece or coupling. In hearing aids of this general character, thequality of the sound presented at the wearers ear is often impaired as aresult of frequency discrimination, which takes place duringtransmission of the sound waves through the flexible sound deliveryconduit tube, and which most usually appears at the car as anoveremphasis of those frequencies at the lower portion of the speechsound spectrum. The magnitude of this apparent over-ernphasis of lowfrequencies depends largely upon the physical characteristics of theflexible sound conduit and the length of the sound conduit, both ofwhich are widely variable, and the latter of which is usually adjustedto suit the requirements of each user. From this it will be seen thatthe variable factors controlling the degree of frequency discriminationtaking place within the flexible sound conduit make it difficult and, inmost cases, impractical to correct the frequency response electricallywithin the amplifier or any point ahead of the reproducer.

It is, therefore, an object of the instant invention to provide a simpleand highly efficient means for correcting the frequency response of theacoustical portion of the hearing aid to compensate for frequencydiscrimination which takes place during transmission of sound wavesthrough the flexible sound delivery conduit from the reproducer orreceiver to the auditory canal of the user. in accordance with theinvention, I accomplish this objective inexpensively and verysatisfactorily by providing one or more restricted vent passages toatmosphere from the acoustical sound delivery system at a place thereinahead of the flexible sound delivery conduit. in practice, it is foundthat venting of the acoustical system to atmosphere produces a frequencydiscrimination in the direction tending to correct for the frequencydiscrimination which takes place within the flexible sound deliveryconduit, and that the degree of such corrective frequency discriminationcan be widely varied by merely varying the total cross-section area ofthe venting passage or passages. In practice, I have found that locatingsuch tone control venting passage or passages ahead of the sounddelivery conduit, rather than at or adjacent the delivery end thereof,results in improved clarity of the sounds delivered to the ear. It isbelieved that this improvement is due to the fact that the tendency toproduce types of distortion other than frequency discrimination isreduced by eliminating from the acoustical system part of the unwantedsound before introduction of the sound into the flexible conduit.

in the preferred embodiment of the invention illustrated, the acousticaltone control comprises a plurality of restricted vent passages and amanually-operative valve mechanism for selectively controlling theopening and 2,754,365 Patented July 10, 1956 ice closing of saidpassages. In fact, in the preferred structure illustrated, the flexiblesound delivery conduit is coupled to the audio reproducer or receiver bya coupling head having an internal cavity in sealed communication withthe interior of the speaker or reproducer casing, and which couplinghead defines the said tone control vent apertures and carries the valvemechanism for manually controlling said passages.

The above and other highly important objects and advantages of theinvention will be made apparent from the following specification, claimsand appended drawings.

In the accompanying drawings, like characters indicate like partsthroughout the several views.

Referring to the drawings:

Fig. l is a view in elevation, with some parts broken away and someparts shown in section, of a wearable electronic hearing aidincorporating a preferred embodiment of the invention, and showing thesame in operative relation to the ear of a hard of hearing personwearing the instrument;

Figs. 2, 3 and 4 are greatly enlarged views in side elevation, with someparts broken away, of the reproducer and associated tone control valvemechanism of Fig. 1, said views respectively showing the tone controlvalve in different adjusted positions;

Fig. 5 is a transverse sectional view, with some parts on the sectionline shown in full and some parts broken away, taken on the line 55 ofFig. 3;

Fig. 6 is a detail sectional View, taken on the line 6-6 of Fig. 4, withsome parts on the section line shown in full;

Fig. 7 is a diagrammatic view graphically illustrating the frequencyresponse of the hearing aid at the users ear in three differentpositions of the tone control valve mechanism; and

Fig. 8 is a diagrammatic view of the main hearing aid components,showing in block-type diagram the amplifier and microphone containedwithin the hearing aid casing shown at the bottom of Fig. 1.

In Fig. l, the ear of a hard of hearing person wearing a hearing aidequipped with the invention is indicated by 1 and part of the clothingof such person is indicated by 2. The main casing or housing of thewearable hearing aid is indicated by full lines at 3 in Fig. l and bycorrespondingly-identified dotted lines in Fig. 8. This main casing orhousing is adapted to be worn in a pocket of the user, or suitablyattached to the clothing of the user by other well-known means notillustrated and contains the usual microphone 4 and electronic audiopower amplifier 5, shown in block diagram in Fig. 87 As shown in Fig. 8,the electrical output end of the microphone 4 is connected to the inputof the amplifier 5 by a pair of leads 6. The electrical output of theamplifier 5 is connected by a pair of flexible lead wires 7 to theremotelylocated audio frequency reproducer or receiver, indicated as anentirety by 8.

As illustrated, the audio reproducer S is of the conventional,miniature, electro-magnetically operated variety, commonly used in thehearing aid industry and comprises telescopically engaged inner andouter casing or housing sections 9 and 10, respectively, containing theusual magnetically responsive diaphragm i1 and electromagnet diaphragmactuating structure 12. In Fig. 5, the winding of the electromagneticstructure 12 is indicated by 13, and it may be assumed that the leads 7from the amplifier 5 are connected thereto. The reproducer housingsection 10 and diaphragm 11 cooperatively define a sound chamber 14 andthe said housing section 10 defines a tubular coupling nipple 15providing a sound outlet passage 16 from the sound chamber 14.Preferably, and as illustrated, the coupling nipple 15 is reduced in gdiameter inwardly of its outer end to provide a lock ring receivingchannel 17 (see Figs. 5 and 6).

The acoustical output of the reproducer or receiver 8 is connected tothe auditory canal of one of the users ears 1 through the sound outletpassage 16, a flexible sound delivery tube or conduit 18, a couplinghead 19, and an ear piece coupling 2 The ear piece or coupling is of theconventional moulded type and defines a coupling nipple 21 that isadapted to be inserted into the auditory canal of the associated ear tomake sealed communication therewith. The flexible sound conduit 8 may beof various different materials, but is usually formed of a suitableplastic material having suitable flexibility and color characteristics.The coupling head 19 is bored to provide an internal cavity 22, whichreceives the coupling nipple 15 (see Figs. 5 and 6) and defines anextension of the sound chamber 14 of the reproducer 8. The coupling head19 is detachably locked on the coupling nippl 15 by means of aconventional split lock ring 23, contained within a channel 24 of thecoupling head 19 and seated in the channel 17 of the coupling nipple 15.The internal cavity or chamber 22 of the coupling head 19 is sealed fromatmosphere by a resilient gasket 24 interposed between the adjacent flatsurfaces of the coupling head 19 and reproducer housing section 10. Asound outlet passage 25 is provided from the cavity or chamber 22 of thecoupling head 19 by a coupling nipple 26, which is telescopically fittedto the adjacent end of the flexible sound outlet conduit 18, as bestshown in Fig. 1 By further reference to Fig. 1, it will be seen that thereproducer or receiver 8 is adapted to be supported from the Wearersclothing 2 by attached chain links or the like 27 and a pin or the like28.

In the preferred embodiment of the invention illustrated, the acousticaltone control comprises two vent passages or orifices through thecoupling head 19 from its internal cavity or sound chamber 22,respectively indicated by 29 and 3t), and a manually-operated valve 31for controlling the said vent passages 29 and 30. The valve 31 is adisc-like elementmounted on the flat outer face of the coupling head 19by means of a headed mounting and locking screw 32 disposed coaxiallythereof and the head 19 and having threaded engagement with the latter.The vent orifices or passages 29 and 30 underlie the valve disc 31 andare disposed in circumferentiallyspaced relation about the axis of thevalve disc 31. The valve disc 31 is provided with a pair ofcircumferentiallyspaced passages, respectively indicated by 33 and 34,arranged for cooperative registration with the vent passages 29 and 31).When the screw 32 is tight, the valve disc 33 is locked againstaccidental movement and the adjacent faces thereof and the head 19 makeair-tight sealing engagement.

By reference to Figs. 1, 2, 3 and 4, it will be seen that the valve disc31 is provided with a position-indicating arrow for cooperation withposition-indicating numerals 1, 2, and 3 arranged incircumferentially-spaced relation on the outer face of the coupling head19. By reference to Fig. 2, it will be noted that when the valve disc ispositioned with its arrow 35 opposite the numeral 1 of the couplinghead, the valve disc orifices or passages 33 and 34 are both out ofregistration with the coupling head or vent passages 29 and 30, so thatthe coupling head pasages 23 and 30 are both closed. By reference toFig. 3, it will be seen that when the valve disc arrow 35 is inregistration with the numeral 2 of the coupling head, the valve discorifice 34 is in registration with the coupling head vent passage 29,while the coupling head vent passage 30 remains closed. By reference toFig. 4, it will be seen that when theval've disc 31 is positioned withits arrow 35 opposite the numeral 3 of the coupling head, the valve discorifice'34 is in'registration with the coupling head orifice 30 and thevalvediscorifice 33 is in registration'with the coupling vent passage ororifice 29: In each ofthese'threedifferent positions 'of the tone 4-control valve disc 31, shown respectively in Figs. 2, 3 and 4, a tonequality or response characteristic of the sound presented to the usersear will be different, as clearly illustrated graphically in Fig. 7.

By reference to Fig. 7, horizontal lines on the graph represent soundpressure response characteristics in decibels (db) and vertical linesindicate different frequencies Within the speech sound spectrum incycles per second (C. P. S On this graph of Fig. 7, the full line curvemarked Position 1, indicates the response characteristic at the usersear of the hearing aid when the valve disc 31 is in position 1, asindicated in Fig. 2; the broken line curve marked Position 2, indicatesthe response characteristic of the hearing aid when the tone controlvalve disc 31 is in position 2, as shown in Fig. 3; and the dotted linecurve marked Position 3 indicates the response characteristic of thehearing aid when the valve disc 31 is in position 3, as shown in Fig. 4.Otherwise stated, curve position 1 illustrates the acoustical responsewhen both of the vent passages 29 and 30 are closed; curve position 2illustrates the acoustical response characteristic of the instrumentwhen the vent passage 29 is open and the vent passage 30 is closed; andcurve position 3 illustrates the acoustical response of the instrumentwhen the vent passages 29 and 30 are both fully opened. Of course, itwill be understood that response characteristics intermediate thoseshown may be obtained by partially opening or closing one or both of thepassages 29 and 30. It will be understood that these responsecharacteristics are representative of What may be expected when theelectrical output of the amplifier is substantially uniform throughoutthe speech sound spectrum, and that the apparent over-emphasis of thelow frequency portion of the spectrum between the cycles per second andabout 700 cycles per second is due to frequency discrimination in theacoustical portion of the system represented by the flexible sounddelivery condit 18. Of course, this over-emphasis of low frequencieswill prove very unnatural and undesirable to many hearing aid users, butmay prove desirable to some users whose hearing is particularlydeficient in the low frequency portion of the speech frequency spectrum.Most hard of hearing persons will find the sound characteristics mostdesirable when the tone control valve disc 31 is in one of positions 2or 3, which produce a progressive attenuation of the otherwiseover-emphasized low frequencies, and produce a much closer approach to auniform amplification of all frequencies within the speech soundspectrum. It will, of course, be obvious that greater low frequencyattenuation may be provided by further increasing the total area of thevent passage or passages.

My invention has been thoroughly tested and found to be entirelyadequate for the accomplishment of the objectives set forth; and, whileI have shown a preferred embodiment of my invention, it will beunderstood that the same is capable of modification without departurefrom the spirit and scope of the invention as defined in the claims.

What I claim is:

1. An electrically-operated audio reproducer for use as part of aWearable hearing aid and adapted to be worn by a hard of hearing personin a position remote from an auditory canal of such person, saidreproducer being of the air conduction type and comprising a casingdefining the sound outlet passage, a coupling head detachably applied tothe exterior of the reproducer casing and having an internal cavity insealed communication with the outlet passage of the reproducer, aflexible sound delivery conduit leading from the coupling head and beingin sealed communication with the internal cavity thereof, the extendedend of said flexible sound conduit being adapted to be coupled to theauditory canal of a person wearing the hearing aid, and means for'attenuating 'low frequency sound wavesdelivered by the reproducer to theflexible sound conduit to'conipensate for frequency discriminationwithin the flexible sound delivery conduit, said means comprising arestricted venting passage from the internal cavity of the coupling headto atmosphere.

2. An electrically-operated audio reproducer for use as part of awearable hearing aid and adapted to be worn by a hard of hearing personin a position remote from an auditory canal of such person, saidreproducer being of the air conduction type and comprising a casingdefining the sound outlet passage, a coupling head detachably applied tothe exterior of the reproducer casing and having an internal cavity insealed communication with the outlet passage of the reproducer, aflexible sound delivery conduit leading from the coupling head and beingin sealed communication with the internal cavity thereof, the extendedend of said flexible sound conduit being adapted to be coupled to theauditory canal of a person wearing the hearing aid, and means forattenuating low frequency sound waves delivered by the reproducer to theflexible sound conduit to compensate for frequency discrimination Withinthe flexible sound delivery conduit, said means comprising a restrictedventing passage from the internal cavity of the coupling head toatmosphere, and a manually-operated valve for opening and closing saidpassage.

3. An electrically-operated audio reproducer for use as part of awearable hearing aid and adapted to be worn by a hard of hearing personin a position remote from an auditory canal of such person, saidreproducer being of the air conduction type and comprising a casingdefining he sound outlet passage, a coupling head detachably applied tothe exterior of the reproducer casing and having an internal cavity insealed communication with the outlet passage of the reproducer, aflexible sound delivery conduit leading from the coupling head and beingin sealed communication with the internal cavity thereof, the extendedend of said flexible sound conduit being adapted to be coupled to theauditory canal of a person wearing the hearing aid, and means forattenuating low frequency sound waves delivered by the reproducer to theflexible sound conduit to compensate for frequency discrimination withinthe flexible sound delivery conduit, said means comprising a pluralityof restricted venting passages from the internal cavity of the couplinghead to atmosphere, and a manuallyoperated valve associated with thecoupling head for selectively opening and closing said passages.

4. An electrically operated audio reproducer for use as part of awearable hearing aid and adapted to be worn by a hard of hearing personin a position remote from an auditory canal of such person, saidreproducer being of the air conduction type and comprising anelectromagnetically operated diaphragm, a casing structure enclosing thediaphragm and defining a sound chamber in communication with one side ofthe diaphragm, and a sound outlet passage leading from said chamber, aflexible sound delivery conduit coupled to said chamber through saidpassage, the extended end of said flexible sound conduit being adaptedto be coupled to the auditory canal of a person wearing the hearing aid,and means for attenuating the low frequency sound waves delivered by thereproducer to the flexible sound conduit to compensate for frequencydistortion within the flexible sound delivery conduit, said meanscomprising a restricted venting passage from said sound chamber toatmosphere.

5. An electrically operated audio reproducer for use as part of awearable hearing aid and adapted to be worn by a hard of hearing personin a position remote from an auditory canal of such person, saidreproducer being of the air conduction type and comprising anelectromagnetically operated diaphragm, a casing structure enclosing thediaphragm and defining a sound chamber in communication with one side ofthe diaphragm, and a sound outlet passage leading from said chamber, aflexible sound delivery conduit coupled to said chamber through saidpassage, the extended end of said flexible sound conduit being adaptedto be coupled to the auditory canal of a person wearing the hearing aid,means for attenuating the low frequency sound waves delivered by thereproducer to the flexible sound conduit to compensate for frequencydistortion within the flexible sound delivery conduit, said meanscomprising a restricted venting passage from said sound chamber toatmosphere, and a manually operated valve for opening and closing saidrestricted venting passage.

References Cited in the file of this patent UNITED STATES PATENTS1,915,358 Giles June 27, 1933 2,215,585 Huenlich Sept. 24, 19402,271,467 Smithline Jan. 27, 1942 2,505,124 Lepeschkin Apr. 25, 19502,506,981 Weaver et a1 May 9, 1950 2,541,164 Huenlich Feb. 13, 1951

